Almost every weapon you obtain in DOOM will have optional upgrades you can pursue via mods and upgrades for your weapons. Most weapons have one or two mods that can be obtained by interacting with the many Field Drones you can find in each level.

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After obtaining the mods, you can upgrade them with additional perks requiring points gained from finding secrets, completing challenges, and through other means. There's an additional master upgrade that can only be upgraded once a specific challenge has been completed.

Your character's Praetor Suit can be further upgrades to enhance your abilities beyond normal capabilites. By finding and obtaining tokens from dead Elite Guards, you can modify your suit to be better at dexterity, discovery, and equipment effectiveness.

Other upgrades can be obtained by using Argent Cells to increase your health, armor, and ammo capabilities.

As you progress through the game, you may come upon large green glowing Runes that denote a Rune Challenge. Completing this unique challenge will reward you with a specialized rune that increases your capabilities, though only a certain number of runes can be used at a time. Each rune can be further upgraded to be even more effective, if certain challenges have been met.